Pressure gauge for vehicle tires

ABSTRACT

A tire pressure gauge apparatus for securing to a vehicle tire valve stem mounted to a tire valve stem port in a vehicle tire, the valve stem including a tubular stem body containing a valve assembly having a valve opening mechanism, the stem body having a stem connection end fitting sealingly to the tire valve stem port, and having a stem air receiving end, the apparatus including a housing for placement in fluid communication with received air from within the tire contained within the tire valve stem; a structure for opening the valve opening mechanism; and a pressure equilibration structure dividing the housing into a received air chamber and a biasing air chamber and including a pressure indicator element, the pressure equilibration structure and the pressure indicator element being movable relative to the housing, and the pressure indicator element displaying a pressure reading of received air from within the tire which varies with the position of the pressure equilibration structure relative to the housing; so that alteration of the pressure of received air within the received air chamber from the valve stem causes movement of the equilibration structure within the housing to re-establish pressure equilibrium between biasing air sealed within the biasing air chamber and received air within the received air chamber, and movement of the equilibration structure causes the indicator element to move relative to the housing to provide a received air pressure reading.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the fields of tires and tirepressure gauges. More specifically the present invention relates to anair pressure gauge apparatus which is combined with a tire valve stem toremain on the stem and continuously display the tire pressure, so thatat any moment the user can see at a glance whether the tire is properlyinflated, and thus know at a glance whether the tire is safe andproviding optimum tire wear and fuel efficiency. The gauge apparatuspreferably is combined with the valve stem either by screwing it ontoexisting external cap threads of the valve stem and letting it remainattached until momentary removal during tire inflation, or byintegrating it permanently into the structure of the valve stem duringstem manufacture.

The essential elements of the apparatus include an apparatus housing,containing a received air chamber for placement in fluid communicationwith received air from within a vehicle tire and containing a biasingair chamber containing a fixed quantity of biasing air, the chambersbeing sealingly separated from each other by a pressure equilibrationstructure which includes a pressure indicator element. The pressureequilibration structure moves within the housing to alter the relativevolumes of the two chambers and thus to equalize the pressures of thetwo chambers. The pressure indicator element moves relative to theapparatus housing as the equilibration structure moves to equalizechamber pressures to display a tire pressure reading. The gaugeapparatus operates on the principle of continuous re-establishment ofpressure equilibrium, where alteration of received air pressure fromoutside the apparatus, that is, from within the tire, causes movement ofthe pressure equilibration structure within the housing against thetrapped, fixed quantity of biasing air sealed within the biasing airchamber, thereby moving the indicator structure to reveal the pressurereading. The biasing air functions as a fixed standard against whichvarying tire pressure is measured.

2. Description of the Prior Art

There have long been gauges for measuring the pressure of air containedwithin vehicle tires. All of these prior gauges have relied on springsto provide biasing against which a pressure reading is taken. A problemwith such prior gauges is that springs can lose resiliency, can corrode,and can add cost and complexity to the gauges.

These prior, spring biased -gauges include Parker, U.S. Pat. No.4,310,014, issued on Jan. 12, 1982 for a tire pressure indicatorintegral with a tire stem; Yabor, U.S. Pat. No. 4,901,747, issued onFeb. 20, 1990 for a tire inflation valve with a pressure indicator;Hunt, et al., U.S. Pat. No. 4,924,697, issued on May 15, 1990 for atire-mounted air pressure gauge assembly; Huang, U.S. Pat. No.5,014,643, issued on May 14, 1991 for a tire pressure indicator;Rabizadeh, U.S. Pat. No. 5,503,012, issued on Apr. 12, 1996 for a tirepressure monitoring device; Cummings, U.S. Pat. No. 5,569,849, issued onOct. 29, 1996 for a visual tire cap pressure gauge; Wang, U.S. Pat. Np.5,856,619, issued on Jan. 5, 1999 for a tire pressure indicator;Halcomb, U.S. Pat. No. 5,979,232, issued on Nov. 9, 1999 for a tirepressure indicator carried aboard a wheel; Chi, U.S. Pat. No. 5,886,254,issued on Mar. 23, 1999 for a tire valve pressure-indicating coverutilizing colors to indicate tire pressure.

On the other hand, Wong, U.S. Pat. No. 4,384,543, issued on May 24,1983, discloses a air release check valve and indicator device whichautomatically releases air from an over-inflated tire. A criticalproblem with Wong is that the device is inoperative, for multiplereasons. First, air from within a tire stem bearing against the piston19 cannot move piston 19 because its pressure is opposed by equivalentair pressure entering the piston cylinder 16 through port 34. Thus thepiston will not move no matter what tire air pressure is introduced intothe device housing, and the device cannot function either as a pressurerelief valve or as a pressure indicator. Nor can Wong receive air froman air line to fill the tire. Air entering Wong would have no way ofmoving the piston shaft to place its narrower segment within thepartition aperture.

None of the displaceable, pressure measuring structures within the knownprior art gauges are at equilibrium and at rest prior to installation ona tire. All have set points above atmospheric, unlike the gaugeembodiments of the present application:

It is thus an object of the present invention to provide a tire gaugeapparatus which relies on pressure equilibration rather than on amechanical spring to produce a tire pressure reading.

It is another object of the present invention to provide such a gaugeapparatus which remains on the tire and produces an accurate and easilyvisible tire pressure reading.

It is still another object of the present invention to provide such agauge apparatus which can be integrated into a valve step duringmanufacture.

It is yet another object of the present invention to provide such agauge apparatus which is initially at equilibrium with the atmosphere,is always active, which measures both under- and over-inflation, whichcan be constructed with a thin pressure responsive membrane with noelastic force constant, and does not rely on pre-set valves.

It is finally an object of the present invention to provide such a valvestem which is highly economical to manufacture, simple in design, lightweight, compact and highly durable.

SUMMARY OF THE INVENTION

The present invention accomplishes the above-stated objectives, as wellas others, as may be determined by a fair reading and interpretation ofthe entire specification.

A tire pressure gauge apparatus is provided for securing to a vehicletire valve stem mounted to a tire valve stem port in a vehicle tire, thevalve stem including a tubular stem body containing a valve assemblyhaving a valve opening mechanism, the stem body having a stem connectionend fitting sealingly to the tire valve stem port, and having a stem airreceiving end, the apparatus including a housing for placement in fluidcommunication with received air from within the tire contained withinthe tire valve stem; a structure for opening the valve openingmechanism;

and a pressure equilibration structure dividing the housing into areceived air chamber and a biasing air chamber and including a pressureindicator element, the pressure equilibration structure and the pressureindicator element being movable relative to the housing, and thepressure indicator element displaying a pressure reading of received airfrom within the tire which varies with the position of the pressureequilibration structure relative to the housing; so that alteration ofthe pressure of received air within the received air chamber from thevalve stem causes movement of the equilibration structure within thehousing to re-establish pressure equilibrium between biasing air sealedwithin the biasing air chamber and received air within the received airchamber, and movement of the equilibration structure causes theindicator element to move relative to the housing to provide a receivedair pressure reading.

A tire pressure gauge apparatus is further provided for securing to avehicle tire valve stem mounted to a valve stem port in a vehicle tire,the valve stem including a tubular stem body containing a valve assemblyhaving an outwardly biased valve opening shaft, the stem body having astem connection end with a circumferential groove for fitting sealinglyinto an edge of the tire valve stem port, and having a stem airreceiving end having external threads for affixation of a valve stem capand having internal threads into which the valve assembly is screwed,the apparatus including a housing for placement in fluid communicationwith received air from within the tire contained within the tire valvestem; a structure for depressing the valve opening shaft and therebyopening the valve assembly, the structure for depressing being connectedto the housing; and a pressure equilibration structure dividing thehousing into a received air chamber and a biasing air chamber andincluding a pressure indicator element, the pressure equilibrationstructure and the pressure indicator element being movable relative tothe housing, and the pressure indicator element displaying a pressurereading of received air from within the tire which varies with theposition of the pressure equilibration structure relative to thehousing; so that alteration of the pressure of received air within thereceived air chamber from the valve stem causes movement of theequilibration structure within the housing to re-establish pressureequilibrium between biasing air sealed within the biasing air chamberand received air within the received air chamber, and movement of theequilibration structure causes the indicator element to move relative tothe housing to provide a received air pressure reading. The housingpreferably is a tubular housing having an open connection end and aclosed indicator display end, the biasing air chamber including anindicator display window and terminating in an integral housing endwall; and the pressure equilibration structure preferably includes adiaphragm disk and the indicator element includes an indicator cylindermarked with calibrations and secured to the diaphragm disk and extendinginto the biasing air chamber and passing adjacent to the indicatordisplay window, the diaphragm disk being sized in diameter to fit withinthe housing and being sealingly and circumferentially joined to theinner surface of the housing; structure for sealingly securing thediaphragm disk to the step; a valve opening shaft depression structurefor depressing the valve opening shaft to release air from within thetire into the received air chamber; structure for securing the valvestem body to and in fluid communication with the received air chamber;so that the apparatus is screwed onto the stem air receiving end tocreate a seal between the received air chamber and the valve stem body,and so that the valve opening shaft depression structure depresses thevalve opening shaft to an extent which opens the valve assembly to passair from within the tire into the received air chamber and against thediaphragm disk; and so that pressure of received air from within thetire deflects the diaphragm disk toward the biasing air chamber, therebycompressing the biasing air until the pressure of the biasing air risesto equal the pressure of the received air within the received airchamber, whereupon the attached indicator cylinder comes to rest toindicate the pressure of air contained within the received air chamberand within the tire. The calibrations preferably are eithercircumferential color bands or are lines labeled with pressure readingfigures.

The housing once again is preferably a tubular housing having an openconnection end and a closed indicator display end, the biasing airchamber including an indicator display window and an integral housingend wall; and the indicator element preferably includes an indicatorcylinder dividing the biasing air chamber from the received air chamberand being slidably mounted within the housing to slide into and out ofthe biasing air chamber, the indicator cylinder being marked withcalibrations and passing adjacent to the indicator display window; avalve opening shaft depression structure for depressing the valveopening shaft to release air from within the tire into the received airchamber; structure for securing the valve stem body to and in fluidcommunication with the received air chamber; so that the apparatus isscrewed onto the stem air receiving end to create a seal between thereceived air chamber and the valve stem body, and so that the valveopening shaft depression structure depresses the valve opening shaft toan extent which opens the valve assembly to pass air from within thetire into the received air chamber and against the indicator cylinder;and so that pressure of received air from within the tire slides theindicator cylinder into the biasing air chamber, thereby compressing thebiasing air until the pressure of the biasing air within the biasing airchamber rises to equal the pressure of the received air within thereceived air chamber, whereupon the indicator cylinder comes to rest toindicate the pressure of air contained within the received air chamberand within the tire.

The housing once again is preferably a tubular housing having an openconnection end and a closed indicator display end, the biasing airchamber including an indicator display window and terminating in anintegral housing end wall; and the pressure equilibration structurepreferably includes a partition wall having a partition wall air passingport and an indicator bellows secured to the partition wall over thepartition wall air passing port and extending into the biasing airchamber, the indicator bellows being axially expandable into the biasingair chamber, the indicator bellows being marked with calibrations andpassing adjacent to the indicator display window; a valve opening shaftdepression structure for depressing the valve opening shaft to releaseair from within the tire into the received air chamber and into theindicator bellows; structure for securing the valve stem body to and influid communication with the received air chamber; so that the apparatusis screwed onto the stem air receiving end to create a seal between thereceived air chamber and the valve stem body, and such that the valveopening shaft depression structure depresses the valve opening shaft toan extent which opens the valve assembly to pass air from within thetire into the received air chamber and into the indicator bellows; andso that pressure of received air from within the tire expands theindicator bellows into the biasing air chamber, thereby compressing thebiasing air until the pressure of the biasing air within the biasing airchamber rises to equal the pressure of the received air within thereceived air chamber, whereupon the attached indicator bellows ceases toexpand, and indicates the pressure of air contained within the receivedair chamber and tire.

A tire pressure gauge and valve stem apparatus is provided for securinginto a valve stem port in a vehicle tire, including a vehicle tire valvestem having a tubular stem body containing a valve assembly, the stembody having a stem connection end with a structure for fitting sealinglyinto a tire valve stem port, and having a stem air receiving end; agauge housing secured to the valve stem body in fluid communication withreceived air contained within the valve stem body through a valve stembody lateral opening; and a pressure equilibration structure dividingthe housing into a received air chamber and a biasing air chamber andincluding a pressure indicator element, the pressure equilibrationstructure and pressure indicator element being movable relative to thehousing and displaying a pressure reading of received air from withinthe tire which varies with the position of the pressure equilibrationstructure relative to the housing; so that alteration of the pressure ofreceived air within the received air chamber causes movement of thepressure equilibration structure within the housing to re-establishpressure equilibrium between biasing air sealed within the biasing airchamber and received air within the received air chamber, and movementof the equilibration structure causes the indicator element to moverelative to the housing to provide a received air pressure reading. Thehousing is preferably a tubular housing having a connection end securedto a side of the valve stem body and a closed indicator display end, thebiasing air chamber including an indicator display window andterminating in an integral housing end wall; and the pressureequilibration structure preferably includes a diaphragm disk and theindicator element preferably includes an indicator cylinder marked withcalibrations and secured to the diaphragm disk and extending into thebiasing air chamber and passing adjacent to the indicator displaywindow, the diaphragm disk being sized in diameter to fit within thehousing and being sealingly and circumferentially joined to the innersurface of the housing; and structure for sealingly securing thediaphragm disk to the step; so that pressure of received air from withinthe tire deflects the diaphragm disk toward the biasing air chamber,thereby compressing the biasing air until the pressure of the biasingair within the biasing air chamber rises to equal the pressure of thereceived air within the received air chamber, whereupon the attachedindicator cylinder comes to rest to indicate the pressure of aircontained within the received air chamber and within the tire. Thecalibrations once again preferably are either circumferential colorbands or are lines labeled with pressure reading figures.

The housing once again is preferably a tubular housing having aconnection end secured to a side of the valve stem body and a closedindicator display end, the biasing air chamber including an indicatordisplay window and terminating in an integral housing end wall; and theindicator element preferably includes an indicator cylinder dividing thebiasing air chamber from the received air chamber and being slidablymounted within the housing to slide into and out of the biasing airchamber, the indicator cylinder being marked with calibrations andpassing adjacent to the indicator display window; so that pressure ofreceived air from within the tire slides the indicator cylinder into thebiasing air chamber, thereby compressing the biasing air until thepressure of the biasing air within the biasing air chamber rises toequal the pressure of the received air within the received air chamber,whereupon the indicator cylinder comes to rest to indicate the pressureof air contained within the received air chamber and within the tire.Once again, the calibrations preferably are either circumferential colorbands or are lines labeled with pressure reading figures.

The housing once again is preferably a tubular housing having aconnection end and a closed indicator display end, the biasing airchamber including an indicator display window and terminating in anintegral housing end wall; and the pressure equilibration structurepreferably includes a partition wall having a partition wall air passingport and an indicator bellows secured to the partition wall over thepartition wall air passing port and extending into the biasing airchamber, the indicator bellows being axially expandable into the biasingair chamber, the indicator bellows being marked with calibrations andpassing adjacent to the indicator display window; so that pressure ofreceived air from within the tire expands the indicator bellows into thebiasing air chamber, thereby compressing the biasing air until thepressure of the biasing air within the biasing air chamber rises toequal the pressure of the received air within the received air chamber,whereupon the attached indicator bellows ceases to expand and achieves asubstantially fixed position relative to the housing to indicate thepressure of air contained within the received air chamber and within thetire. The tubular housing optionally includes an abrupt reduction indiameter between the connection end and the indicator display enddefining a housing step forming a housing shoulder, so that the housingconnection end is a wider housing tube segment defining the received airchamber and the housing indicator display end is a narrower housing tubesegment defining the biasing air chamber; and the diaphragm disk issecured sealingly against the housing shoulder.

A tire pressure gauge and valve stem apparatus is further provided forsecuring into a valve stem port in a vehicle tire, including a vehicletire valve stem having a tubular stem body containing a valve assembly,the stem body having an outer surface and having a stem connection endwith structure for fitting sealingly into a tire valve stem port, andhaving a stem air receiving end; a gauge housing including a housingcircumferential wall formed of a translucent material and bowedoutwardly from the circumferential wall along the longitudinal axis ofthe housing circumferential wall and wrapped sealingly andcircumferentially around the valve stem body; and the equilibrationstructure preferably is an elastic bladder contained within the housingcircumferential wall and wrapped circumferentially around and sealinglysecured to the outer surface of the tubular stem body; a stem branchpassageway extending laterally from the interior of the stem body andopening within the bladder; and a substantially opaque liquid containedwithin an annular space defined between the bladder and the housingcircumferential wall together with a certain quantity of biasing air;the quantity and pressure of the biasing air and as the elasticresistance of the bladder in relation to the minimum adequate tire airpressure being so that a tire air pressure of at least a certainmagnitude which is deemed adequate causes the bladder to expandradially, to compress the biasing air and to displace the substantiallyopaque liquid and bear against the inner surface of the housingcircumferential wall, making a portion of the bladder visible throughthe housing circumferential wall, and so that a tire air pressure ofless than the certain magnitude deemed adequate permits the elasticityof the bladder and the pressure of the biasing air to retract thebladder from contact with the housing circumferential wall and thesubstantially opaque liquid to flow between the bladder and thecircumferential wall to obscure the bladder from view. The bladderpreferably is brightly pigmented and the opaque liquid is darklypigmented for increased visual contrast between the bladder and theopaque liquid for greater bladder visibility when the bladder bearsagainst the housing circumferential wall. dr

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, advantages, and features of the invention willbecome apparent to those skilled in the art from the followingdiscussion taken in conjunction with the following drawings, in which:

FIG. 1 is a perspective view of the first embodiment of the gaugeapparatus adjacent to the threaded end of a standard valve stem shown inpartial cross-section, also showing the valve stem cap.

FIG. 2 is a cut-away perspective view of the first embodiment of thegauge apparatus showing the fitting structure, diaphragm disk, indicatorelement and calibrated display window.

FIG. 3 is an exploded view of the elements of the first embodiment,revealing the valve opening shaft depression projection structure.

FIG. 4 is a perspective bottom view of the apparatus of the firstembodiment.

FIG. 5 is a cut-away perspective view as in FIG. 2 of the secondembodiment of the gauge apparatus having the expandable bellowsindicator element.

FIG. 6 is an exploded view of the apparatus of FIG. 5.

FIG. 7 is a cut-away perspective view of the third embodiment of thegauge apparatus, having the indicator cylinder slidably protruding intothe narrower housing tube segment.

FIG. 8 is an exploded perspective view of the third embodiment of theapparatus shown in FIG. 5.

FIGS. 9 and 10 are a perspective side view of the combined valve stemand gauge apparatus of the fourth embodiment.

FIG. 11 is a perspective view of the gauge portion of the fourthembodiment of the gauge apparatus which sealingly and engagingly fitsaround the valve stem body, this view revealing the fitting structureand depression projection within the gauge housing.

FIG. 12 is a cross-sectional side perspective view of the gaugeapparatus of the fifth embodiment, showing the expandable bladder andthe stem branch passageway delivering tire air into the gauge housing.

FIG. 12a is another cross-sectional side perspective view of theapparatus of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

Reference is now made to the drawings, wherein like characteristics andfeatures of the present invention shown in the various FIGURES aredesignated by the same reference numerals.

The Invention Generally

Referring to FIGS. 1-12a, an air pressure gauge apparatus 10 isdisclosed which is combined with a tire valve stem 12 to remain on thetire (not shown) and continuously display the tire pressure, so that atany moment the user may stop the vehicle and see at a glance whether thetire is under-, over- or correctly inflated. The gauge apparatus remainsjoined to the vehicle tire while the tire is stationary as well as whilethe tire is rolling. Gauge apparatus 10 preferably is combined with thevalve stem 12 either by screwing it onto existing external cap threads18 a of the valve stem 12 and letting it remain attached until momentaryremoval during tire inflation, or by integrating it permanently into thestructure of the valve stem 12 itself during stem manufacture.

The essential elements of apparatus 10 include an apparatus housing 30,containing a received air chamber 32 for placement in fluidcommunication with received air from within a vehicle tire andcontaining a biasing air chamber 34 containing a fixed quantity ofbiasing air, the chambers 32 and 34 being sealingly separated from eachother by a pressure equilibration structure 50 which includes a pressureindicator element 52. The pressure equilibration structure 50 moveswithin the housing 30 to alter the relative volumes of the two chambers32 and 34 and thus to equalize the pressures of these two chambers. Thepressure indicator element 52 moves relative to the apparatus housing 30as the equilibration structure 50 moves to equalize chamber 32 and 34pressures to display a tire pressure reading.

Gauge apparatus 10 operates on the principle of continuousre-establishment of pressure equilibrium, where alteration of receivedair pressure from outside apparatus 10, that is, from within the tire,causes movement of the indicator element 52 within the housing 30against the trapped, fixed quantity of biasing air sealed within thebiasing air chamber 34. The biasing air functions as a fixed andconstant standard against which varying tire pressure is measured. Thepressure of the biasing air exerts a force against a biasing air chamberside of equilibration structure 50, while the received air exerts acounterbalancing force against the opposing, received air chamber sideof equilibration structure 50. A change in received pressure alters theforce against one side of equilibration structure 50, so that pressurefrom the biasing air on the other side of the equilibration structure 50must increase or decrease to offset and thus re-establish equilibriumabout the equilibration structure 50.

To increase the biasing air pressure, the equilibration structure 50must move a certain distance to compress the biasing air to a certainextent, and this movement of equilibration structure 50 correspondinglyalters the tire pressure magnitude displayed by the indicator element52. To decrease the biasing air pressure, the equilibration structure 50must move a certain distance to decompress the biasing air to a certainextent, and by the same token this movement of equilibration structure50 correspondingly alters the tire pressure magnitude displayed byindicator element 52.

First Preferred Embodiment

A first embodiment of the inventive gauge apparatus 10 is removablysecured to the existing tire valve stem 12. See FIG. 1. A standard tirevalve stem 12 includes a tubular stem body 14 containing an axialpassageway 12 a and a standard valve assembly 20 having an outwardlybiased valve opening shaft 22. The stem body 14 has a tire connectionend 16 with a circumferential groove 16 a which snaps firmly andsealingly into the edge of a tire valve stem port (not shown), and hasan air receiving end 18. The air receiving end 18 typically is made ofmetal and has external threads 18 a for affixation of a valve stem cap24 and internal threads into which the valve assembly 20 is screwed.

The gauge apparatus 10 includes a tubular housing 30 having an openhousing connection end 36 and a closed indicator display end 38. SeeFIGS. 2-3. The housing 30 abruptly reduces in diameter between the twoends 36 and 38 to define a primary housing step 42, so that the housingconnection end 36 is a wider housing tube segment 30 a and the housingindicator display end 38 is a narrower housing tube segment 30 b. Thehousing indicator display end 38 includes a transparent indicatordisplay window 44 and terminates in an integral housing end wall 46. Anintermediate, secondary housing step 48 is optionally provided betweenthe wider and narrower housing tube segments 30 a and 30 b.

For one version, the equilibration structure 50 includes diaphragm disk54 with an indicator element in the form of an indicator cylinder 52secured to its biasing air chamber face. The diaphragm disk 54 is sizedin diameter to fit closely within the wider housing tube segment 30 ainner diameter and sealingly fits against the shoulder defined byprimary housing step 42, so that indicator cylinder 52 extends into thebiasing air chamber 34 and passes beside the indicator display window44. Either or both of the indicator cylinder 52 and the window 44 aremarked with calibrations 56 so that any given position of the indicatorcylinder 52 relative to the window 44 aligns a calibration and thusdefines a pressure reading. The reading may be a color indicatingunderpressurization, overpressurization or proper pressurization of thetire, so that the calibrations 56 are three differently coloredcircumferential bands extending around the indicator cylinder 52.Alternatively, calibrations 56 may be numbered line segments or dots ondisplay window 44 indicating actual pressure readings, such as in poundsper square inch. See FIG. 2.

A fitting structure 60 is provided including an internally threadedfitting tube 62 having a fitting structure partition wall 64 with an airdelivery passageway 66 passing therethrough and axially through a valveopening shaft depression projection 68 and an external diametersubstantially matching the wider housing tube segment 30 a innerdiameter is fitted into the wider housing tube segment 30 a until itabuts the diaphragm disk 54 to seal the disk 54 against the primary step42 shoulder. See FIG. 4. Shaft depression projection 68 has a diametricgroove 72 across its free end to permit released tire air to flowbetween the abutting valve opening shaft 22 and shaft depressionprojection 68 into passageway 66. Notches 74 are provided in the fittingstructure 60 rim for engagement by a tool (not shown) for insertion ofthe fitting structure 60 into the wider housing tube segment 30 a duringmanufacture. Then fitting structure 60 exterior surface is sealinglysecured to the wider housing tube segment 30 a inner surface, such as bymelding or with an appropriate glue.

Apparatus 10 is screwed onto the air receiving end 18 of the valve stembody 14 so that a seal is created between the apparatus 10 and the valvestem body 14, and so that the shaft depression projection depresses 68the valve opening shaft 22 against the biasing of the valve assembly 20internal spring (not shown) to an extent which opens the valve assembly20 to pass air from within the tire into the housing received airchamber 32, through the air delivery passageway 66, and against thediaphragm disk 54. The pressure of the air from the tire, i.e. thereceived air, deflects the diaphragm disk 54 toward the biasing airchamber 34, compressing the biasing air until the biasing air pressurerises to equal the tire air pressure. At this moment of equilibrium, thediaphragm 54 and the attached indicator cylinder 52 come to rest. Thecalibrations 56 registering in the display window 44 when indicatorcylinder 52 comes to rest indicate the pressure of the air within thetire, either in terms of under- or over- or correct inflation, or interms of an actual pressure measurement expressed in force per squareunit of area.

Second Preferred Embodiment

In a second embodiment, the diaphragm disk 54 is eliminated, and anindicator element in the form of an expandable indicator bellows 86 isattached to the partition wall 64 and protruding into biasing airchamber 34. See FIGS. 5 and 6. Air delivery passageway 66 in partitionwall 64 is widened to pass received air from the tire into indicatorbellows 86. The expansion or contraction of indicator bellows 86 intothe biasing air chamber 34 brings the tire air and biasing air pressuresinto equilibrium. The position of the indicator bellows 86 relative tothe display window 44 determines which calibration 56 registers in thedisplay window 44 and thereby indicates the tire air pressure.

Third Preferred Embodiment

In a third embodiment, cylinder 52 is rigid and slidably mounted withinnarrower housing tube segment 30 b. See FIGS. 7-8. Once again, diaphragmdisk 54 is eliminated for this embodiment. The cylinder 52 sealingly andslidably moves within narrower housing tube segment 30 b, so thatbiasing air is compressed between the cylinder 52 and the walls ofbiasing air chamber 34. As in the previous variations, the cylinder 52is marked with calibrations 56 of either type previously described,which register with the display window 44 to indicate the tire pressure.

Fourth Preferred Embodiment

A fourth embodiment is provided which incorporates the elements of thefirst embodiment, but the gauge apparatus 10 is manufactured as anintegral part of the valve stem 120. See FIGS. 9-11. The housingconnection end 136 is sealingly secured to a side of the valve stem body140 and protrudes radially outward from valve stem body 140. The housingconnection end 136 may be formed integrally with a circumferentialhousing extension 182 having a port 184 into which the stem body 140 issealingly fitted. A stem branch passageway 142 extends radially from theinterior of stem 120 and opens into the housing connection end 136. Itis further contemplated, that the elements of the second and thirdembodiments may also be incorporated into a valve stem 120 duringmanufacture, also by securing housing connection end 136 sealingly tothe side of valve stem body 140 and providing a stem branch passageway142 opening into the housing connection end 136.

Fifth Preferred Embodiment

A fifth embodiment is provided, once again in which the gauge apparatus10 is manufactured as an integral part of the valve stem 212. See FIGS.12-12a. The housing 230 for this embodiment is an annular structurehaving a housing circumferential wall 232 through which the tubular stembody 240 is axially and sealingly fitted and secured. Circumferentialwall 232 is formed of either transparent or translucent material. Withinthe housing 230, wrapping circumferentially around and sealingly securedto the tubular valve stem body 240 outer surface is an outwardly archedand elastic bladder 250, which preferably is brightly colored. A stembranch passageway 242 extends radially from the interior of the stem 212and opens within the bladder 250. A dark, opaque liquid 252 is providedin the annular space between the bladder 250 and the housingcircumferential wall 232, with a certain quantity of trapped, biasingair also continued within this annular space. The volume and pressure ofthe biasing air as well as the elastic resistance of the bladder 250 areselected during manufacture in relation to a given minimum adequate tireair pressure, so that when the tire air pressure is adequate the annularcentral region of bladder 250 bears against the housing circumferentialwall 232 and thus becomes visible through the displaced dark, opaqueliquid 252. In the event of tire deflation to a pressure below thegiven, minimum value for safe and proper tire wear, the bladder 250elastically contracts to recede radially inward and thus move out ofcontact housing circumferential wall 232, so that the opaque liquid 252passes between the wall 232 and the bladder 250 and obscures the bladder250 from view. The clearly notable absence of the bright bladder 250band bearing against the housing circumferential wall 232 alerts thevehicle operator of hazardously low tire air pressure, without theoperator having to access or use any tool. As the operator adds air tothe tire, he or she can watch the housing circumferential wall and knowthat adequate tire pressure is reached when the bright band of thebladder 250 midsection abuts the wall 232 and thereby becomes visible.

The remainder of the tire stem 212 is conventional. As mentioned above,it includes a tubular stem body 214 containing a standard valve assembly220 having an outwardly biased valve opening shaft 222. The stem body214 has a tire connection end 216 preferably including a circumferentialgroove 216 a which snaps firmly and sealingly into the edge of a tirevalve stem port, and has an air receiving end 218. The air receiving end218 preferably is made of metal and has external cap threads 218 a foraffixation of a valve stem cap 224 and internal threads into which thevalve assembly 220 is screwed.

While the invention has been described, disclosed, illustrated and shownin various terms or certain embodiments or modifications which it hasassumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

We claim:
 1. A tire pressure gauge apparatus for securing to a vehicletire valve stem mounted to a tire valve stem port in a vehicle tire, thevalve stem including a tubular stem body containing a valve assemblyhaving a valve opening means, the stem body having a stem connection endfitting sealingly to the tire valve stem port, and having a stem airreceiving end, the apparatus comprising: a housing for placement influid communication with received air from within the tire containedwithin the tire valve stem; means for opening said valve opening means;and a pressure equilibration structure dividing said housing into areceived air chamber and a biasing air chamber and comprising a pressureindicator element, said pressure equilibration structure and saidpressure indicator element being progressively movable relative to saidhousing and thereby substantially continuously maintaining andre-establishing pressure equilibrium between air within said receivedair chamber and air within said biasing air chamber, and said pressureindicator element displaying a pressure reading of received air fromwithin the tire which varies with the position of said pressureequilibration structure relative to said housing; such that alterationof the pressure of received air within said received air chamber fromthe valve stem causes movement of said equilibration structure withinsaid housing to re-establish pressure equilibrium between biasing airsealed within said biasing air chamber and received air within saidreceived air chamber, and movement of said equilibration structurecauses said indicator element to move relative to said housing toprovide a received air pressure reading.
 2. A tire pressure gaugeapparatus for securing to a vehicle tire valve stem mounted to a valvestem port in a vehicle tire, the valve stem including a tubular stembody containing a valve assembly having an outwardly biased valveopening shaft, the stem body having a stem connection end with acircumferential groove for fitting sealingly into an edge of the tirevalve stem port, and having a stem air receiving end having externalthreads for affixation of a valve stem cap and having internal threadsinto which the valve assembly is screwed, the apparatus comprising: ahousing for placement in fluid communication with received air fromwithin the tire contained within the tire valve stem; means fordepressing said valve opening shaft and thereby opening said valveassembly, said means for depressing being connected to said housing; anda pressure equilibration structure dividing said housing into a receivedair chamber and a biasing air chamber and comprising a pressureindicator element, said pressure equilibration structure and saidpressure indicator element being progressively movable relative to saidhousing, and thereby substantially continuously maintaining andre-establishing pressure equilibrium between air within said receivedair chamber and air within said biasing air chamber and said pressureindicator element displaying a pressure reading of received air fromwithin the tire which varies with the position of said pressureequilibration structure relative to said housing; such that alterationof the pressure of received air within the received air chamber from thevalve stem causes movement of said equilibration structure within thehousing to re-establish pressure equilibrium between biasing air sealedwithin said biasing air chamber and received air within said receivedair chamber, and movement of said equilibration structure causes saidindicator element to move relative to said housing to provide a receivedair pressure reading.
 3. The gauge apparatus of claim 2, wherein saidhousing is a tubular housing having an open connection end and a closedindicator display end, said biasing air chamber including an indicatordisplay window and terminating in an integral housing end wall; andwherein said pressure equilibration structure comprises a diaphragmpanel and said indicator element comprises an indicator cylinder markedwith calibrations and secured to said diaphragm panel and extending intosaid biasing air chamber and passing adjacent to said indicator displaywindow, said diaphragm panel being sized in diameter to fit within saidhousing and being sealingly and circumferentially joined to the innersurface of said housing; means for sealingly securing said diaphragmpanel to said step; valve opening shaft depression means for depressingthe valve opening shaft to release air from within the tire into saidreceived air chamber; means for securing the valve stem body to and influid communication with said received air chamber; such that theapparatus is screwed onto the stem air receiving end to create a sealbetween said received air chamber and the valve stem body, and such thatthe valve opening shaft depression means depresses the valve openingshaft to an extent which opens the valve assembly to pass air fromwithin the tire into said received air chamber and against saiddiaphragm panel; and such that pressure of received air from within thetire deflects said diaphragm panel toward said biasing air chamber,thereby compressing the biasing air until the pressure of the biasingair rises to equal the pressure of the received air within the receivedair chamber, whereupon the attached indicator cylinder comes to rest toindicate the pressure of air contained within said received air chamberand within the tire.
 4. The gauge apparatus of claim 3, wherein saidcalibrations are circumferential color bands.
 5. The gauge apparatus ofclaim 3, wherein said calibrations are lines labeled with pressurereading figures.
 6. The gauge apparatus of claim 2, wherein said housingis a tubular housing having an open connection end and a closedindicator display end, said biasing air chamber including an indicatordisplay window and an integral housing end wall; and wherein saidindicator element comprises an indicator cylinder dividing said biasingair chamber from said received air chamber and being slidably mountedwithin said housing to slide into and out of said biasing air chamber,said indicator cylinder being marked with calibrations and passingadjacent to said indicator display window; valve opening shaftdepression means for depressing the valve opening shaft to release airfrom within the tire into said received air chamber; means for securingthe valve stem body to and in fluid communication with said received airchamber; such that the apparatus is screwed onto the stem air receivingend to create a seal between said received air chamber and the valvestem body, and such that the valve opening shaft depression meansdepresses the valve opening shaft to an extent which opens the valveassembly to pass air from within the tire into said received air chamberand against said indicator cylinder; and such that pressure of receivedair from within the tire slides said indicator cylinder into saidbiasing air chamber, thereby compressing the biasing air until thepressure of the biasing air within the biasing air chamber rises toequal the pressure of the received air within the received air chamber,whereupon the indicator cylinder comes to rest to indicate the pressureof air contained within said received air chamber and within the tire.7. The gauge apparatus of claim 2, wherein said housing is a tubularhousing having an open connection end and a closed indicator displayend, said biasing air chamber including an indicator display window andterminating in an integral housing end wall; and wherein said pressureequilibration structure comprises a partition wall having a partitionwall air passing port and an indicator bellows secured to said partitionwall over said partition wall air passing port and extending into saidbiasing air chamber, said indicator bellows being axially expandableinto said biasing air chamber, said indicator bellows being marked withcalibrations and passing adjacent to said indicator display window;valve opening shaft depression means for depressing the valve openingshaft to release air from within the tire into said received air chamberand into said indicator bellows; means for securing the valve stem bodyto and in fluid communication with said received air chamber; such thatthe apparatus is screwed onto the stem air receiving end to create aseal between said received air chamber and the valve stem body, and suchthat the valve opening shaft depression means depresses the valveopening shaft to an extent which opens the valve assembly to pass airfrom within the tire into said received air chamber and into saidindicator bellows; and such that pressure of received air from withinthe tire expands said indicator bellows into said biasing air chamber,thereby compressing the biasing air until the pressure of the biasingair within said biasing air chamber rises to equal the pressure of thereceived air within said received air chamber, whereupon the attachedindicator bellows ceases to expand, and indicates the pressure of aircontained within said received air chamber and tire.
 8. A tire pressuregauge and valve stem apparatus for securing into a valve stem port in avehicle tire, comprising: a vehicle tire valve stem comprising a tubularstem body containing a valve assembly, said stem body having a stemconnection end with means for fitting sealingly into a tire valve stemport, and having a stem air receiving end; a gauge housing secured tosaid valve stem body in fluid communication with received air containedwithin said valve stem body through a valve stem body lateral opening;and a pressure equilibration structure dividing said housing into areceived air chamber and a biasing air chamber and comprising a pressureindicator element, said pressure equilibration structure and pressureindicator element being progressively movable relative to said housingand thereby substantially continuously maintaining and re-establishingpressure equilibrium between air within said received air chamber andair within said biasing air chamber and displaying a pressure reading ofreceived air from within the tire which varies with the position of thepressure equilibration structure relative to the housing; such thatalteration of the pressure of received air within the received airchamber causes movement of said pressure equilibration structure withinthe housing to re-establish pressure equilibrium between biasing airsealed within said biasing air chamber and received air within saidreceived air chamber, and movement of said equilibration structurecauses said indicator element to move relative to said housing toprovide a received air pressure reading.
 9. The apparatus of claim 8,wherein said housing is a tubular housing having a connection endsecured to a side of said valve stem body and a closed indicator displayend, said biasing air chamber including an indicator display window andterminating in an integral housing end wall; and wherein said pressureequilibration structure comprises a diaphragm panel and said indicatorelement comprises an indicator cylinder marked with calibrations andsecured to said diaphragm panel and extending into said biasing airchamber and passing adjacent to said indicator display window, saiddiaphragm panel being sized in diameter to fit within said housing andbeing sealingly and circumferentially joined to the inner surface ofsaid housing; and means for sealingly securing said diaphragm panel tosaid step; such that pressure of received air from within the tiredeflects said diaphragm panel toward said biasing air chamber, therebycompressing the biasing air until the pressure of the biasing air withinthe biasing air chamber rises to equal the pressure of the received airwithin the received air chamber, whereupon the attached indicatorcylinder comes to rest to indicate the pressure of air contained withinsaid received air chamber and within the tire.
 10. The gauge apparatusof claim 9, wherein said calibrations are circumferential color bands.11. The gauge apparatus of claim 9, wherein said calibrations are lineslabeled with pressure reading figures.
 12. The gauge apparatus of claim8, wherein said housing is a tubular housing having a connection endsecured to a side of said valve stem body and a closed indicator displayend, said biasing air chamber including an indicator display window andterminating in an integral housing end wall; and wherein said indicatorelement comprises an indicator cylinder dividing said biasing airchamber from said received air chamber and being slidably mounted withinsaid housing to slide into and out of said biasing air chamber, saidindicator cylinder being marked with calibrations and passing adjacentto said indicator display window; such that pressure of received airfrom within the tire slides said indicator cylinder into said biasingair chamber, thereby compressing the biasing air until the pressure ofthe biasing air within the biasing air chamber rises to equal thepressure of the received air within the received air chamber, whereuponthe indicator cylinder comes to rest to indicate the pressure of aircontained within said received air chamber and within the tire.
 13. Thegauge apparatus of claim 12, wherein said calibrations arecircumferential color bands.
 14. The gauge apparatus of claim 12,wherein said calibrations are lines labeled with pressure readingfigures.
 15. The gauge apparatus of claim 8, wherein said housing is atubular housing having a connection end and a closed indicator displayend, said biasing air chamber including an indicator display window andterminating in an integral housing end wall; and wherein said pressureequilibration structure comprises a partition wall having a partitionwall air passing port and an indicator bellows secured to said partitionwall over said partition wall air passing port and extending into saidbiasing air chamber, said indicator bellows being axially expandableinto said biasing air chamber, said indicator bellows being marked withcalibrations and passing adjacent to said indicator display window; suchthat pressure of received air from within the tire expands saidindicator bellows into said biasing air chamber, thereby compressing thebiasing air until the pressure of the biasing air within said biasingair chamber rises to equal the pressure of the received air within saidreceived air chamber, whereupon the attached indicator bellows ceases toexpand and achieves a substantially fixed position relative to saidhousing to indicate the pressure of air contained within said receivedair chamber and within the tire.
 16. A tire pressure gauge and valvestem apparatus for securing into a valve stem port in a vehicle tire,comprising: a vehicle tire valve stem comprising a tubular stem bodycontaining a valve assembly, said stem body having an outer surface andhaving a stem connection end with means for fitting sealingly into atire valve stem port, and having a stem air receiving end; a gaugehousing comprising a housing circumferential wall formed of atranslucent material and bowed outwardly from said circumferential wallalong the longitudinal axis of said housing circumferential wall andwrapped sealingly and circumferentially around said valve stem body; andwherein said equilibration structure is an elastic bladder containedwithin said housing circumferential wall and wrapped circumferentiallyaround and sealingly secured to the outer surface of said tubular stembody; a stem branch passageway extending laterally from the interior ofsaid stem body and opening within said bladder; and a substantiallyopaque liquid contained within an annular space defined between saidbladder and said housing circumferential wall together with a certainquantity of biasing air; the quantity and pressure of the biasing airand the elastic resistance of said bladder in relation to the minimumadequate tire air pressure being such that a tire air pressure of atleast a certain magnitude which is deemed adequate causes said bladderto expand radially, to compress the biasing air and to displace saidsubstantially opaque liquid and bear against the inner surface of saidhousing circumferential wall, making a portion of said bladder visiblethrough said housing circumferential wall, and such that a tire airpressure of less than the certain magnitude deemed adequate permits theelasticity of said bladder and the pressure of said biasing air toretract said bladder from contact with said housing circumferential walland said substantially opaque liquid to flow between said bladder andsaid circumferential wall to obscure said bladder from view.
 17. Theapparatus of claim 16, wherein said bladder is brightly pigmented andwherein said opaque liquid is darkly pigmented for increased visualcontrast between said bladder and said opaque liquid for greater bladdervisibility when said bladder bears against said housing circumferentialwall.
 18. The apparatus of claim 3, wherein said tubular housingcomprises an abrupt reduction in diameter between said connection endand said indicator display end defining a housing step forming a housingshoulder, such that said housing connection end is a wider housing tubesegment defining said received air chamber and said housing indicatordisplay end is a narrower housing tube segment defining said biasing airchamber; and wherein said diaphragm panel is secured sealingly againstsaid housing shoulder.
 19. The apparatus of claim 6, wherein saidtubular housing comprises an abrupt reduction in diameter between saidconnection end and said indicator display end defining a housing step,such that said housing connection end is a wider housing tube segmentdefining said received air chamber and said housing indicator displayend is a narrower housing tube segment defining said biasing airchamber.
 20. The apparatus of claim 9, wherein said tubular housingcomprises an abrupt reduction in diameter between said connection endand said indicator display end defining a housing step forming a housingshoulder, such that said housing connection end is a wider housing tubesegment defining said received air chamber and said housing indicatordisplay end is a narrower housing tube segment defining said biasing airchamber; and wherein said diaphragm panel is secured sealingly againstsaid housing shoulder.